The present invention relates broadly to an analog circuit apparatus and in particular to an offset reduction apparatus for eliminating DC offsets in an output signal.
In many prior art circuits, such as analog/digital converters, an analog input signal level is established and then processed through various gains, switches or stages to produce a resultant analog output signal or error signal. In the most common application of the analog/digital converter, the converter is used to transform information into a form suitable for processing on a digital computer. This requires that analog information must be quantized into discrete voltage signals having an assigned logical 0 or 1 level (for example, ground or +5 volts). The raw information frequently is taken from measurements of temperatures, forces, shaft rotations, or other continuous quantities and is first represented by an analog electrical signal, which is then converted to digital. The effect of this processing is often sufficiently different from the ideal effect -- due to dc offsets caused by switches, amplifier offsets, etc. -- to introduce significant errors. In many cases where the output or error signal is not required continuously, these undesirable effects may be greatly reduced, often to a substantially negligible amount, by the present invention which is described herein.